SUMMARY
Strange-looking horizontal stripe in konsole when find bar is open

STEPS TO REPRODUCE
1. Put some text in konsole (probably most obvious with lots of '|')
2. Press Ctrl+Shift+F to open the find bar.
3. Switch to another window and optionally switch back (doesn't have to be covering the konsole window).

OBSERVED RESULT
A strange-looking horizontal stripe meeting at the bottom of the find bar.

EXPECTED RESULT
No strange-looking horizontal stripe meeting at the bottom of the find bar.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: 
KDE Plasma Version: 5.14.3
KDE Frameworks Version: 5.52.0
Qt Version: 5.11.1

ADDITIONAL INFORMATION
for (( x = 0; x < 1000; ++x)) ; do echo -n '||||||||||' ; done